This type of printers used for operation with both kinds of paper have been very inadequate up to now. They are very loud, particularly during the endless paper operation, since on the one hand the noise of the printing mechanism comes out through the openings arranged on the top side of the printer housing, and since on the other hand the noise of the conveying unit as well as of the paper, which tends to chatter especially in rapid printer operation, penetrate to the outside. For this reason the openings not required each time must be especially covered. Besides this, for endless paper operation the feed rolls not required for the conveying of the paper must be lifted off. For this reason the reconversion of the printing apparatus for one or the other mode of operation is very expensive. Besides this, there is the possibility of an erroneous servicing of the apparatus, since nothing can be seen from the outside as to which mode of operation the printing apparatus is currently situated in.